The invention relates to an encapsulated high-voltage apparatus insulated by sulfur hexafluoride which has at least one electric conductor of aluminum or an aluminum alloy and which carries the high voltage and is braced to the encapsulation by means of parts made of insulating material.
In encapsulated high-voltage devices such as metal-encapsulated, gas-insulated high-voltage lines, it is known to brace the electric conductors to the preferably grounded, electrically conducting encapsulation by means of parts made of insulating material. The conductors consist of aluminum or an aluminum alloy and carry the high voltage. In connection with such high-voltage lines, reference may be had to Deutsche Offenlegungsschrift No. 2,118,176.
Also, in metal-encapsulated high-voltage switch gear with a gaseous insulating means such as sulfur hexafluoride, the high voltage conductors may consist of aluminum. In case of fault conditions, in particular in the case of a breakdown of the dielectric, an arc forms between the electric conductor carrying the high voltage and the outer encapsulation which leads, at least in the places where it remains for any length of time, to a high thermal stress of the high-voltage apparatus and may also lead to an additional stress of the encapsulation and of the electric conductor due to the selection of an aluminum material as the material of the electric conductor, the aluminum being desirable for cost reasons.
Under the action of a standing arc, and the heating in the area of the arc associated therewith, not only are the metal parts heated, but if the sulfur hexafluoride is used as the insulating gas, components of this insulating gas are dissociated. Above a certain critical temperature, the fluorine split off from the sulfur hexafluoride will react with the aluminum, the chemical reaction being exothermic. Therefore, a chemical process is initiated which can lead to the destruction of the high-voltage apparatus even after the extinction of the electric arc because the initiated exothermic chemical process can lead to the further dissociation of the insulating gas thereby endangering the high-voltage apparatus.
Accordingly, it is an object of the invention to provide an encapsulated, gas-insulated high-voltage apparatus which affords increased resistance to direct or indirect arc action.